There is uncertainty regarding the efficacy of androgen deprivation therapy for earlier stages of prostate cancer. In addition, there are serious toxicities and a substantial financial cost associated with this therapy, particularly with the use of gonadotropin-releasing hormone (GnRH) agonists, which are now the predominant form of androgen deprivation. [unreadable] [unreadable] In the face of these concerns, recent studies have shown a dramatic rise in the use of GnRH agonists for prostate cancer over the 1990s, even in settings where there is no evidence of survival benefit. Wide differences in rates of GnRH agonist use between geographic regions suggest the presence of variations in practice patterns, possibly reflecting provider uncertainty about the risks and benefits of this therapy. [unreadable] [unreadable] We hypothesize that the provider plays an important role in influencing the observed time trends and variations in use of GnRH agonists for prostate cancer. This study will use linked SEER Medicare data and American Medical Association data to achieve the following objectives: 1) describe the variation among providers in use of GnRH agonists, 2) examine the effect of provider characteristics on the likelihood of use of GnRH agonists for prostate cancer and 3) determine the provider characteristics that influenced the change in use of GnRH agonists for prostate cancer over the 1990s. [unreadable] [unreadable] Collectively, the information derived from this proposal will help direct efforts at provider education and monitoring the use of GnRH agonists for prostate cancer. This will be especially important as more information on the risks and benefits of GnRH agonists become available, with the ultimate goal being the provision of quality care for men with prostate cancer. [unreadable] [unreadable] [unreadable]